Cofactors, Coenzymes and Prosthetic Groups
- Are substances other than substrates and inhibitors that interact with enzymes
- They allow some enzymes to function properly.
Cofactors
- The inorganic ions that an enzyme requires to function.
- Some inorganic ions help to stabilise the structure of the enzyme or may actually
take part in the reaction at the active site.
o E.g. chloride ions act as a cofactor for amylase
Coenzymes
- Larger organic cofactors are coenzymes
- Some coenzymes are permanently bound to the enzyme they assist, either in or near
the active site.
- Some only bind temporarily
- They link different enzyme catalysed reactions into a sequence during metabolic
processes.
- Vitamins are a good source of coenzymes. For example vitamin B group contains
o Pantothenic acid, a key component of coenzyme A
o Nicotinic acid to produce coenzymes NAD and NADP.
o Vitamin B used to produce the coenzyme FAD
Examples of coenzyme functions
- During many reactions in respiration, coenzymes NAD and FAD are reduced and
oxidised transferring energy in the form of H+ ions.
- Coenzyme NADP does the same thing in chloroplasts in photosynthesis
- Coenzymes ATP and coenzyme A act differently, by transferring chemical groups
o ATP transfers phosphate groups between respiration and energy consuming
processes in cells
o Coenzyme A is responsible for the transfer of an acetyl group from fatty acids
and glucose during respiration.
Prosthetic groups
- Are substances other than substrates and inhibitors that interact with enzymes
- They allow some enzymes to function properly.
Cofactors
- The inorganic ions that an enzyme requires to function.
- Some inorganic ions help to stabilise the structure of the enzyme or may actually
take part in the reaction at the active site.
o E.g. chloride ions act as a cofactor for amylase
Coenzymes
- Larger organic cofactors are coenzymes
- Some coenzymes are permanently bound to the enzyme they assist, either in or near
the active site.
- Some only bind temporarily
- They link different enzyme catalysed reactions into a sequence during metabolic
processes.
- Vitamins are a good source of coenzymes. For example vitamin B group contains
o Pantothenic acid, a key component of coenzyme A
o Nicotinic acid to produce coenzymes NAD and NADP.
o Vitamin B used to produce the coenzyme FAD
Examples of coenzyme functions
- During many reactions in respiration, coenzymes NAD and FAD are reduced and
oxidised transferring energy in the form of H+ ions.
- Coenzyme NADP does the same thing in chloroplasts in photosynthesis
- Coenzymes ATP and coenzyme A act differently, by transferring chemical groups
o ATP transfers phosphate groups between respiration and energy consuming
processes in cells
o Coenzyme A is responsible for the transfer of an acetyl group from fatty acids
and glucose during respiration.
Prosthetic groups
